This invention relates to an internal combustion engine, and more particularly, to an improved control device for an exhaust gas recycled internal combustion engine.
It has recently been discovered that low speed running of an internal combustion engine can be significantly improved by delivering a major portion of the engine charge requirements to the chamber through a relatively small cross-sectional area auxiliary induction system. With such an arrangement, turbulence in the combustion chamber at the time of combustion is significantly increased so as to promote the rate of flame propagation. The increased combustion rate not only permits an increase in vehicle economy, but also provides for more effective exhaust gas emission control. The auxiliary induction system supplements a relatively conventional main induction system that supplies the engine charge requirements at higher load rangements. In this way, volumetric efficiency of the engine and maximum power output are not significantly affected.
It has also been the practice with internal combustion engines to employ exhaust gas recirculation (Egr) to improve the control of nitrous oxides in the exhaust gases. Conventional engines are, however, extremely sensitive to the amount of Egr and, as a result, poor running conditions are particularly prevalent with conventional engines employing Egr systems.
Because of its increased flame propagation, the use of the auxiliary induction system may normally require alteration in the spark timing of the engine from a conventional curve. With conventional engines, idle and off-idle spark timing must be considerably advanced due to the slow rate of combustion in the chamber. On the other hand, the use of the auxiliary induction system increases flame speed and results in a spark advance requirement retarded from normal spark timing when the auxiliary induction system is in use.
It is, therefore, a principal object of this invention to provide a control device for an exhaust gas recycled internal combustion engine that offers improved performance, particularly at low speeds with conventional spark timing devices.
It is another object of this invention to provide an induction system for an internal combustion engine using main and auxiliary induction systems and in which exhaust gas recirculation is employed only when the auxiliary induction system is providing a substantial portion of the engine charge requirements.
The introduction of exhaust gases into the combustion chamber with combustion engines significantly retards the rate of combustion in the chamber. Thus, with conventional engines, it is necessary to control the spark timing of the engine in relation to the amount of exhaust gases recirculated. It is extremely difficult, if not impossible, to provide such a spark timing control.
It is, therefore, a further object of this invention to provide a means for controlling the rate of combustion in relation to the amount of exhaust gases recirculated.
It is another object of this invention to provide an induction system for an internal combustion engine in which exhaust gases are recirculated to the chamber only through an auxiliary induction system which increases turbulence and thus compensates for the retarded rate of combustion caused by the exhaust gas recirculation.